Generally, a transparent conductive layer has been used as an essential component of electric and electronic devices such as a power source in display devices, an electromagnetic wave shielding film in home appliances, a transparent electrode in various display fields such as a liquid crystal display (LCD), an organic light emitting diodes (OLED), a field emission display (FED), a plasma display panel (PDP), a flexible display, an electronic paper, or the like. Currently, as a material of the transparent conductive layer, a conductive inorganic oxide material such as indium-tin oxide (ITO), antimony-tin oxide (ATO), antimony-zinc oxide (AZO), or the like, is mainly used.
The transparent conductive layer having relatively high conductivity and transmittance may be produced using the material by a sputtering method, an ion beam method, a vacuum deposition method, or the like, that are generally used. However, in this method, cost for investing into vacuum equipments is high, and it is difficult to mass-produce the transparent conductive layer and prepare a large size transparent conductive layer. Particularly, this method has a limitation in a transparent substrate requiring a low temperature process, such as a plastic film.
At the time of deposition by the sputtering method, a composition of the transparent conductive layer may be changed according to the conditions such as oxygen partial pressure, a temperature, and the like, and the transmittance and resistance of the thin film may be rapidly changed.
Therefore, a method for producing a transparent conductive film performed by coating a layer using a wet coating method such as a spin coating method, a spray coating method, a dip coating method, a printing method, or the like, which are appropriate for low cost and a large size, and then firing the coated layer, or the like, has been suggested. For example, a transparent conductive layer using a metal fine particle and a binder is disclosed in Korean Patent Laid-Open Publication No. 1999-011487, a composition for a transparent conductive layer in which a hollow carbon nano fiber is added to tin oxide is disclosed in Korean Patent Laid-Open Publication No. 1999-064113, and a coating solution for a transparent conductive light selectively absorbing film in which neodymium oxide is added to tin oxide or indium oxide is disclosed in Korean Patent Laid-Open No. 2000-009405. In addition, a method for preparing a solution for a transparent conductive layer containing a metal particle such as gold, silver, or the like, is disclosed in Japanese Patent Laid-open Publication No. 2003-213441.
A surface resistance of the transparent conductive layer produced by the above-mentioned methods is high, time-dependent changes, such as an increase in the surface resistance according to the change in the surroundings and time, or the like, are generated therein, such that initial conductivity may not be maintained. Therefore, this transparent conductive film has a limitation in being used as the transparent conductive layer due to low transmittance In addition, productivity may also decrease since the processes are complicated and various.